package com.accumulate.business.utils;

import java.io.IOException;
import java.io.InputStream;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

public class MD5 {
	private final static String[] hexDigits = {"0", "1", "2", "3", "4", "5", "6", "7",
			"8", "9", "a", "b", "c", "d", "e", "f"};

	/**
	 * 转换字节数组为16进制字串
	 * @param b 字节数组
	 * @return 16进制字串
	 */
	public static String byteArrayToHexString(byte[] b) {
		StringBuilder resultSb = new StringBuilder();
		for (byte aB : b) {
			resultSb.append(byteToHexString(aB));
		}
		return resultSb.toString();
	}

	/**
	 * 转换byte到16进制
	 * @param b 要转换的byte
	 * @return 16进制格式
	 */
	private static String byteToHexString(byte b) {
		int n = b;
		if (n < 0) {
			n = 256 + n;
		}
		int d1 = n / 16;
		int d2 = n % 16;
		return hexDigits[d1] + hexDigits[d2];
	}

	/**
	 * MD5编码
	 * @param origin 原始字符串
	 * @return 经过MD5加密之后的结果
	 */
	public static String MD5Encode(String origin) {
		String resultString = null;
		try {
			resultString = origin;
			MessageDigest md = MessageDigest.getInstance("MD5");
			resultString = byteArrayToHexString(md.digest(resultString.getBytes()));
		} catch (Exception e) {
			e.printStackTrace();
		}
		return resultString;
	}

	/**
	 * 获取该输入流的MD5值
	 *
	 * @param is
	 * @return
	 * @throws NoSuchAlgorithmException
	 * @throws IOException
	 */
	public static String getMD5(InputStream is) throws NoSuchAlgorithmException, IOException {
		StringBuffer md5 = new StringBuffer();
		MessageDigest md = MessageDigest.getInstance("MD5");
		byte[] dataBytes = new byte[1024];

		int nread = 0;
		while ((nread = is.read(dataBytes)) != -1) {
			md.update(dataBytes, 0, nread);
		};
		byte[] mdbytes = md.digest();

		// convert the byte to hex format
		for (int i = 0; i < mdbytes.length; i++) {
			md5.append(Integer.toString((mdbytes[i] & 0xff) + 0x100, 16).substring(1));
		}
		return md5.toString();
	}
}
